Collapse of trophic‐niche structure in belowground communities under anthropogenic disturbance

Abstract

The niche concept is a central paradigm in ecology, but empirical evidence on how the niche structure of belowground communities is affected by ecosystem disturbance is lacking. Niche differentiation evolves due to stable coexistence of species in a community, suggesting that in unstable communities, the niches of species should largely overlap. Here, we test this prediction using empirical data on the trophic‐niche structure of several belowground collembolan communities of natural (forest and meadow) and disturbed (pasture and urban lawn) habitats. Scaled stable isotope compositions of carbon and nitrogen were used to reveal the trophic specialization of species. In full agreement with the theoretical predictions, trophic‐niche structure collapsed in disturbed habitats, which was illustrated by decreased interspecific and increased intraspecific variation in the stable isotope compositions. In stable natural habitats, different trophic niches are occupied by different collembolan species, but in disturbed habitats, poor niche specialization is partly compensated for by intraspecific trophic flexibility. The simplification of food‐web structure was in line with the evidence coming from disturbed aquatic ecosystems, suggesting that the collapse of trophic‐niche structure may be a common feature of disturbed communities across biomes.

Trophic niche differentiation and utilisation of food resources in Collembola is altered by rainforest conversion to plantation systems

“…Variations in Δ 13 C values among Collembola species were more pronounced in rainforest and jungle rubber than in rubber and oil palm plantations. Korotkevich et al (2018) also found the interspecific (in contrast to intraspecific) variation in trophic niches of Collembola to be higher in natural (forest and meadows) than in disturbed habitats (pastures and lawns). Among the Collembola species studied Δ 13 C values of Pseudosinella sp.1 in rainforest, and Callyntrura sp.1 and Sphyroteca sp.1 in jungle rubber differed significantly from those of other Collembola species indicating that these species are able to exploit resources not available to the other Collembola species in the respective land-use system.…”

“…Notably, the narrow range was due to both the lack of high trophic level (predators, scavengers) and low trophic level species (primary decomposers, specialized lichen feeders). This may reflect the dominance of generalist species in the disturbed habitat of oil palm plantations ( Korotkevich et al, 2018 ). Nematode communities also indicated oil palm plantations to be the most disturbed of the four land-use systems studied ( Krashevska et al, 2019 ).…”

“…Different basal resources available in different land-use systems result in changes in trophic niches of decomposer and predatory soil invertebrates, and results in reduced abundance of primary decomposers and in soil animals shifting their feeding habits towards herbivory ( Klarner et al, 2017 ; Krause et al, 2019 ; Susanti et al, 2019 ). Land-use change may also result in reduced trophic niche differentiation among species in belowground communities ( Korotkevich et al, 2018 ), but this has not been investigated in tropical ecosystems.…”

Quantifying temporal variation in dietary niche to reveal drivers of past population declines

“…For spotted skunks, the loss of a central dietary resource may have triggered a clear increase in the isotopic diversity of prey items taken. Declines in primary resources often result in increased dietary niche width for generalist foragers as alternative resources are increasingly incorporated (Korotkevich et al., 2018; Svanback & Persson, 2004; Wilson & Turelli, 1986). This trophic plasticity might allow individuals to incorporate novel resources, which can result in population growth and increased density; similarly, loss of high‐quality resources can incur fitness consequences (Hobart et al., 2019).…”

“…Quantifying alterations in the position and shape of the niche over temporal or spatial scales can reveal otherwise hidden attributes contributing to population decline (Manlick et al., 2019; Rossman et al., 2016; Swanson et al., 2015; Yeakel et al., 2013). For example, reduced availability of critical resources might be evidenced by an increase in intraspecific variation in niche space for generalist species as alternative resources are used (Korotkevich et al., 2018; Svanback & Persson, 2004; Wilson & Turelli, 1986).…”